The neuropeptide oxytocin has been thought of as an "affiliation hormone," because it plays a key role in the formation of adult pair-bonds and initiation of maternal behavior in non-human mammals. Investigators have speculated that oxytocin makes positive social contact more rewarding or increases social sensitivity. There is evidence that oxytocin regulation differs in those with specific psychiatric conditions (e.g., depression, obsessive-compulsive disorder) compared to controls. Little research has been conducted on this hormone with respect to its potential role in social behavior and psychological adjustment in humans, particularly post-partum adjustment. Basic research is needed on the characteristics of OT plasma and its correlates in healthy adults. Levels of plasma OT and the frequency of pulses in plasma oxytocin will be assessed in 40 healthy women of varying ethnicity and between the ages of 21 and 30. It is hypothesized that: (1) There will be a greater number of OT pulses during a positive emotional state than during a negative emotional state; (2) Participants who evidence an OT pulse during a positive emotional state will report more intense subjective feelings of happiness related to the emotional state than will women who do not have an OT pulse at that time; (3) Participants who evidence an OT pulse during the negative emotion induction will report less intense subjective feelings of sadness related to the emotional state than those who do not; (4) Participants who evidence an OT pulse during the positive emotion induction will have more positive emotional traits and attachment-promoting traits (e.g., fewer interpersonal problems; more accepting attachment figures) than those who do not; (5) Participants who evidence an OT pulse at any time during the experiment will have higher mean prolactin levels. Healthy participants will be recruited through flyers at local universities with ethnically diverse populations. Procedures will be conducted at the General Clinical Research Center at UCSF. Using an indwelling catheter, blood draws of 5 ml each will occur every 5 minutes for 110 minutes. There will be a baseline period, a positive emotion induction, an interim period, and a negative emotion induction. Emotion inductions will be accomplished through the standard Relived Emotions Task. Participants will also complete standard questionnaires on perceptions of childhood relationships with parents, emotional traits, personality, and psychological adjustment. Data will be analyzed using computer programs for hormone pulse detection.